This application claims the priority of European Patent Application No. 00 108 732.9 filed Apr. 22, 2000, which is incorporated herein by reference.
The invention relates to an injection steam generator for small appliances, in particular irons or ironing stations.
A known or proposed injection steam generator of this type in particular consists of a thick-walled, heated, preferably cylinder-shaped and upright steam chamber with a water injection nozzle that is arranged outside of the steam chamber and can be moved back and forth perpendicular to the cylinder casing wall (German Patent 298 190 24.9 or European Patent 99 121 229.1). To satisfy the demand for steam, the water injection nozzle, in the following simply called nozzle, moves toward the steam chamber under the effect of the inside or inner pressure generated by a pump in a nozzle chamber. In its end position, the nozzle closes off an injection opening in the steam chamber, and by seating itself to form a seal such that it is pressure tight. In this nozzle position, a predetermined amount of water is sprayed through the injection opening into the heated steam chamber, from which a corresponding amount of steam is then released. After satisfying the demand for steam, the nozzle can be moved automatically back to the starting position. To prevent condensation water from forming in the area immediately surrounding the injection steam generator, particularly inside the housing where the generator is installed, a silicon tube is arranged between the nozzle and the outer steam chamber wall to catch residual steam that sprays from the injection opening when the nozzle is moved back and to guide this steam toward the outside. The nozzle penetrates the silicon tube on the nozzle side so as to be steam-tight. On the opposite side, the tube is attached with an opening to the injection opening, so as to form a steam-tight seal. The end sections of the silicon tube extend into areas adjacent to the injection steam generator, which can hold the residual steam without problems, for example, in a water supply container below the nozzle, into which the condensate formed by the residual steam can flow as well. A non-flexible tube can also be used in place of the silicon tube, which has an outer wall opening through which a cylindrical section of the nozzle can glide steam-tight back and forth.
However, none of these embodiments can prevent the release of residual water from the nozzle as a result of the shrinking volume of the nozzle chamber when the nozzle moves back after the demand for steam is satisfied. This residual water wets the nozzle and runs down into a wastewater catch basin with relatively large dimensions. During a subsequent operating cycle, the residual water leaving the nozzle also wets the hot nozzle sealing seat around the injection opening, which causes the nozzle sealing seat in the steam chamber wall to calcify after several operating cycles, so that the seal around the nozzle is no longer completely tight. Furthermore, the design freedom for an appliance with an injection steam generator of this type is limited by the forcibly low arrangement of the wastewater catch basin below the nozzle or a water supply container that is provided in its place.
Thus, it is the object of the present invention to provide an injection steam generator of the aforementioned generic type, in which no calcification of the nozzle opening, the injection opening and the surrounding nozzle sealing seat occurs, due to residual water from the nozzle chamber.
The above object generally is achieved according to the present invention by an injection steam generator for small appliances, in particular irons or ironing stations, which injection generator comprises: a steam chamber inside a steam generator housing that is provided with an injection opening; a displaceable nozzle positioned telescopically on a fixed member so as to jointly define a nozzle chamber. The nozzle can be displaced, in a first pressure range, in the direction of the injection opening by an inside pressure in the nozzle chamber and can be moved back from the injection opening by a restoring force, in particular a restoring spring, when the interior pressure in the nozzle chamber is in a second pressure range lower than the first pressure range. An arrangement is provided for discharging the residual water from the injection steam generator when the nozzle is moved back from the injection opening. This discharge arrangement includes a drain passage, connected via a valve arrangement with the fixed member and in communication with the nozzle chamber, for discharging the excessive residual water from the nozzle chamber when the nozzle is moved back, with the valve arrangement being designed such that it closes the drain passage in the first pressure range for the pressure inside the nozzle chamber and opens it in the second pressure range for the pressure inside the nozzle chamber.
As a result of the uncomplicated valve arrangement that connects the nozzle chamber to a drain passage, as well as a suitable dimensioning of the valve arrangement for an automatic control of its function in dependence on the pressure conditions occurring in the nozzle chamber, virtually none of the residual water, that must be removed owing to the shrinking volume of the nozzle when it is moved back, is released from the nozzle opening. The residual water thus cannot wet this nozzle opening as well as the sealing ring during the following operating cycle, but is released through a separate drain passage at a distance from the nozzle opening.
The drain passage can lead to a water supply container that is arranged higher than the valve chamber. As a result, an appliance having such an injection steam generator can be designed freely, without limiting the installation location for the water supply container.
The valve arrangement is dimensioned such that it is closed off without external control while the demand for steam is satisfied, provided an increased pressure exists in the valve chamber during a first pressure range. Thus, only the water to be evaporated leaves the nozzle chamber through the nozzle opening, but no water leaves through the drain passage. The effectiveness of the injection steam generator is therefore not reduced. The valve arrangement does not open until after the demand for steam is satisfied, meaning once the inside or interior pressure in the nozzle chamber drops and assumes values in a second pressure range, which is determined in particular by a restoring spring that moves the nozzle back to its starting position. Thus, the residual water is pushed out almost completely through this valve arrangement during the volume reduction in the nozzle chamber, but not through the nozzle opening, which offers a higher flow resistance.
The arrangement for removing residual water is advantageously combined with an injection steam generator embodiment having a pump with a pump discharge valve arranged on the fixed nozzle member 11. When the pump is in operation, it creates a nozzle chamber inside pressure in the first pressure range of 10-12 bar. The restoring spring is dimensioned such that when the nozzle moves back, a nozzle chamber inside pressure of 5-6 bar is generated, wherein the second pressure range is between 5-6 bar as the upper range limit and atmospheric pressure as the lower range limit. In other words: the valve arrangement closes the valve chamber in a working position determined by the pump operation and opens the valve arrangement if the pressure inside the nozzle chamber is reduced and while in the idle position.
In a first uncomplicated embodiment of the injection steam generator, a diaphragm valve is provided as the valve arrangement, in which a diaphragm forms a valve flap that is closed in the first pressure range in the nozzle chamber and is opened in the second pressure range.
Alternatively, the valve arrangement can be realized with the aid of a spring-loaded ball valve that is closed in the first pressure range counter to the spring load and is opened in the second pressure range with the aid of the spring load.
Two exemplary embodiments of the invention are accordingly described in the following with the aid of a drawing with three Figures, from which further features may follow.